Subintimal recanalization with bio-absorbable stent

ABSTRACT

A recanalization catheter assembly and method for establishing a subintimal pathway around an occlusion in a blood vessel. The recanalization catheter assembly an inflatable balloon structure including a distal anchoring portion configured to expand within a true lumen portion of the blood vessel distal of the occlusion to anchor the recanalization catheter from unintentional movement during expansion of a stent in the subintimal pathway. The expandable stent, such as a bioabsorbable stent, may be configured to promote native tissue regrowth around the stent to create a superficial intimal layer along the subintimal pathway.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/568,903, filed on Dec. 9, 2011, the entire disclosure of which isincorporated herein by reference.

TECHNICAL FIELD

The disclosure is directed to devices and methods for recanalization ofan occluded blood vessel. More particularly, the disclosure is directedto devices and methods for positioning a stent in a created subintimalspace of a blood vessel to form a pathway bypassing an occluded portionof the true lumen of the blood vessel.

BACKGROUND

Chronic total occlusion (CTO) is an arterial vessel blockage thatobstructs blood flow through the vessel, and can occur in both coronaryand peripheral arteries. In some instances, it may be difficult orimpossible to pass through the CTO with a medical device in an antegradedirection to recanalize the vessel. Accordingly, techniques have beendeveloped for creating a subintimal pathway (i.e., a pathway between theintimal and adventitial tissue layers of the vessel) around theocclusion and then re-entering the true lumen of the vessel distal ofthe occlusion in an attempt to recanalize the vessel. Accordingly, it isdesirable to provide alternative recanalization devices and/or methodsof recanalizing a blood vessel in which a CTO is present.

SUMMARY

The disclosure is directed to several alternative designs, materials andmethods of manufacturing medical device structures and assemblies, anduses thereof.

Accordingly, one illustrative embodiment is a recanalization catheterassembly for establishing a subintimal pathway around an occlusion in ablood vessel. The recanalization catheter assembly includes an elongatecatheter shaft extending distally from a hub assembly and an inflatableballoon structure mounted on a distal portion of the catheter shaft. Theinflatable balloon structure is configured to be expanded from adeflated configuration to an inflated configuration with a fluiddelivered to an interior of the inflatable balloon structure through aninflation lumen extending through the catheter shaft. A stent surroundsa body portion of the inflatable balloon structure, with a distalanchoring portion of the inflatable balloon structure positioned distalof the stent. The distal anchoring portion of the inflatable balloonstructure is configured to expand within a true lumen portion of theblood vessel distal of the occlusion to anchor the recanalizationcatheter from unintentional movement during expansion of the stent inthe subintimal pathway.

Another illustrative embodiment is a method of recanalizing a bloodvessel by establishing a subintimal pathway around an occlusion. Themethod includes initially creating a subintimal pathway between aproximal opening into a vessel wall proximal of an occlusion and adistal opening into the vessel wall distal of the occlusion. Anexpandable stent is positioned in the subintimal pathway and then theexpandable stent is expanded in the subintimal pathway. Thereafter,native tissue regrowth is promoted around the stent to create asuperficial intimal layer along the subintimal pathway.

Yet another illustrative embodiment is a method of recanalizing a bloodvessel by establishing a subintimal pathway around an occlusion. Themethod includes initially creating a subintimal pathway between aproximal opening into a vessel wall proximal of an occlusion and adistal opening into the vessel wall distal of the occlusion. Anexpandable stent surrounding a body portion of an inflatable balloonstructure is positioned in the subintimal pathway with a distalanchoring portion of the inflatable balloon structure positioned in atrue lumen portion of the blood vessel distal of the occlusion. Thedistal anchoring portion of the inflatable balloon structure is theninflated in the true lumen portion distal of the occlusion and the bodyportion of the inflatable balloon structure is inflated to expand theexpandable stent in the subintimal pathway. The inflated distalanchoring portion anchors the inflatable balloon structure fromunintentional proximal movement while the stent is expanded in thesubintimal pathway to maintain proper placement of the stent in thesubintimal pathway.

The above summary of some example embodiments is not intended todescribe each disclosed embodiment or every implementation of theaspects of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of the disclosure may be more completely understood inconsideration of the following detailed description of variousembodiments in connection with the accompanying drawings, in which:

FIG. 1 is a side plan view of an exemplary catheter apparatus forrecanalization of a blood vessel;

FIG. 2 is a side plan view of an alternative configuration of the distalportion of the catheter apparatus of FIG. 1;

FIG. 3 is a side plan view of another alternative configuration of thedistal portion of the catheter apparatus of FIG. 1;

FIGS. 4-8 illustrate aspects of an exemplary method for recanalizing anoccluded blood vessel using the catheter apparatus of FIG. 1; and

FIG. 8A is a cross-sectional view taken along line 8A-8A of FIG. 8illustrating a pseudo-lumen including a superficial intima layer.

While the aspects of the disclosure are amenable to variousmodifications and alternative forms, specifics thereof have been shownby way of example in the drawings and will be described in detail. Itshould be understood, however, that the intention is not to limitaspects of the disclosure to the particular embodiments described. Onthe contrary, the intention is to cover all modifications, equivalents,and alternatives falling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the term “about” may be indicative asincluding numbers that are rounded to the nearest significant figure.The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

Although some suitable dimensions, ranges and/or values pertaining tovarious components, features and/or specifications are disclosed, one ofskill in the art, incited by the present disclosure, would understanddesired dimensions, ranges and/or values may deviate from thoseexpressly disclosed.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The detailed description and the drawings, which are notnecessarily to scale, depict illustrative embodiments and are notintended to limit the scope of the disclosure. The illustrativeembodiments depicted are intended only as exemplary. Selected featuresof any illustrative embodiment may be incorporated into an additionalembodiment unless clearly stated to the contrary.

An exemplary recanalization catheter 10 is illustrated at FIG. 1. Therecanalization catheter 10, shown as a stent delivery catheter, mayinclude a main catheter shaft 12 extending from a hub assembly 14 at aproximal end 16 of the catheter shaft 12 to an expandable member, shownas an inflatable balloon structure 20 mounted on a distal portion of thecatheter shaft 12 proximate the distal end 18 of the catheter shaft 12.In some instances, the catheter shaft 12, or a proximal portion thereofproximal of the balloon structure 20 may include a slotted hypotube,such as a spiral slotted hypotube, to provide torsional rigidity and/orpushability of the catheter shaft 12 during use. A stent 40 may bepositioned around a body portion 52 of the balloon structure 20 fordelivery to a target location.

The catheter 10 may be configured to be advanced over a guidewire 22 fordelivery to a remote location in the vasculature of a patient. Forexample, in some instances the catheter 10 may be configured as asingle-operator-exchange (SOE) catheter having a guidewire lumenextending from a distal port 26 to a proximal guidewire port 28 locateda short distance proximal of the balloon structure 20 and distal of thehub assembly 14. In such a configuration, the guidewire 22 may extendthrough the guidewire lumen between the distal port 26 and the proximalport 28, and extend along an exterior of the catheter shaft 12 proximalof the proximal port 28 to the proximal end 16 of the catheter shaft 12.In other instances, the catheter 10 may be configured as anover-the-wire (OTW) catheter having a guidewire lumen extending throughthe entire length of the catheter shaft 12 from a distal port 26 at adistal tip of the catheter 10 to a proximal guidewire port 30 in the hubassembly 14. FIG. 1 illustrates such a configuration with the proximallyextending portion of the guidewire 22 in dashed lines. It is noted thatin instances in which the catheter 10 is an SOE catheter, the hubassembly 14 may not include a proximal guidewire port 30 and/or ininstances in which the catheter 10 is an OTW catheter, the proximalguidewire port 28 may not be present. In other instances, the catheter10 may be configured as a fixed-wire catheter having a steerable wireportion forming the distalmost extent of the catheter 10.

The catheter shaft 12 may also include an inflation lumen extending froman inflation port 34 of the hub assembly 14 to an interior of theballoon structure 20. The inflation lumen may be configured fordelivering inflation fluid to the balloon structure 20 to inflate theballoon structure 20, or portions thereof, during a medical procedure.In some instances, the catheter shaft 12 may include a plurality ofinflation lumens in fluid communication with separate inflatableportions of the balloon structure 20 such that individual portions ofthe balloon structure 20 may be inflated independently.

In some embodiments, the catheter shaft 12, or a portion thereof, mayinclude an outer tubular member and an inner tubular member extendingthrough the outer tubular member and defining the guidewire lumen. Thespace between the inner tubular member and the outer tubular member maydefine the inflation lumen. In such embodiments, the main catheter shaft12 may be configured such that the proximal waist of the balloonstructure 20 is secured to the distal end of the outer tubular member,while the distal waist of the balloon structure 20 is secured to thedistal end of the inner tubular member, extending through the interiorof the balloon structure 20.

In other embodiments, the catheter shaft 12, or a portion thereof, maybe an extruded shaft having a plurality of lumens formed therein. Forexample, the extruded shaft may include the guidewire lumen and theinflation lumen extending in a side-by-side arrangement. In suchembodiments, the main catheter shaft 12 may be configured such that theproximal waist of the balloon structure 20 is secured to a portion ofthe extruded shaft, while the distal waist of the balloon structure 20is secured to another portion of the extruded shaft or a tubular memberextending therefrom, extending through the interior of the balloonstructure 20.

The catheter 10 may also include a distal tip 38 extending distally fromthe balloon structure 20. The distal tip 38 may have a lumen extendingtherethrough and opening out to the distal port 26 at the distal endthereof to accommodate the guidewire 22 extending from the distal port26. In some instances, the distal tip 38 may be an atraumatic tip, suchas a flexible, low durometer tip similar to tips provided with typicalangioplasty balloon catheters. However, in other embodiments, the distaltip 38 may be configured to facilitate piercing and/or dissection oftissue layers of the blood vessel. For example, the distal tip 38 mayinclude a sharp, rigid and/or piercing feature. In one embodiment, asshown in FIG. 1, the distal tip 38 may include an angled distal edge,providing the distal tip 38 with a sharpened cutting or piercing edge.

As noted above, the recanalization catheter 10 may be a stent deliverycatheter 10 configured to deliver a stent 40 to a subintimal pathwayformed in a vessel wall to bypass an occlusion. As used herein, the term“stent” is intended to include stents, covered stents, stent-grafts,grafts and other expandable prosthetic devices for implantation in abody passageway to support the passageway. The stents may beself-expanding, expanded by an internal radial force (e.g., throughinflation of a balloon), or a combination of self-expanding and balloonexpandable.

The stent 40, or portions thereof, may be formed of a bioabsorbablematerial. Some exemplary bioabsorbable metallic materials include ironmagnesium alloys. Some exemplary bioabsorbable polymeric materialsinclude polylactide (PLA), poly-L-lactide (PLLA), poly-D-lactide (PDLA),polyglycolide (PGA), polycaprolactone, polydioxanone, and tyrosinepolycarbonate. Some exemplary bioabsorbable stent configurations aredisclosed in U.S. Pat. Nos. 7,699,887; 7,637,940; 7,594,928; 6,719,934,the disclosures of which are herein incorporated by reference in theirentirety.

In some embodiments, the stent 40 may include a covering, such as abioabsorbable poly(lactic-co-glycolic acid (PLGA) membrane, on theabluminal (i.e., radially outward) and/or luminal (i.e., radiallyinward) surface of the stent 40. The covering may create a lesstraumatic interface between the vessel tissue and the stent 40 and/orenhance native tissue regrowth around the stent 40. In some instances,the covering may absorb at a different rate (e.g., faster or slower)than the material forming the stent structure itself. Additionally oralternatively, the covering on the abluminal surface may create a smoothlumen for advancing additional medical devices and medical devicestructures through the stent 40 once implanted.

In some instances, the stent covering may include a lubricant and/orbiological coating to promote tissue growth and/or may include atherapeutic agent for delivery to the target location and subsequenteluding from the coating.

The terms “therapeutic agents,” “drugs,” “bioactive agents,”“pharmaceuticals,” “pharmaceutically active agents”, and other relatedterms may be used interchangeably herein and include genetic therapeuticagents, non-genetic therapeutic agents, and cells. Therapeutic agentsmay be used singly or in combination. A wide range of therapeutic agentloadings can be used in conjunction with the devices of the presentinvention, with the pharmaceutically effective amount being readilydetermined by those of ordinary skill in the art and ultimatelydepending, for example, upon the condition to be treated, the nature ofthe therapeutic agent itself, the tissue into which the dosage form isintroduced, and so forth.

Some specific beneficial agents include anti-thrombotic agents,anti-proliferative agents, anti-inflammatory agents, anti-migratoryagents, agents affecting extracellular matrix production andorganization, antineoplastic agents, anti-mitotic agents, anestheticagents, anti-coagulants, vascular cell growth promoters, vascular cellgrowth inhibitors, cholesterol-lowering agents, vasodilating agents, andagents that interfere with endogenous vasoactive mechanisms.

More specific agents include paclitaxel, sirolimus, everolimus,tacrolimus, Epo D, dexamethasone, estradiol, halofuginone, cilostazole,geldanamycin, ABT-578 (Abbott Laboratories), trapidil, liprostin,Actinomcin D, Resten-NG, Ap-17, abciximab, clopidogrel, Ridogrel,beta-blockers, bARKct inhibitors, phospholamban inhibitors, and Serca 2gene/protein, resiquimod, imiquimod (as well as other imidazoquinolineimmune response modifiers), human apolioproteins (e.g., AI, AII, AIII,AIV, AV, etc.), vascular endothelial growth factors (e.g., VEGF-2), aswell a derivatives of the forgoing, among many others.

Numerous additional therapeutic agents useful for the practice of thepresent invention may be selected from those described in paragraphs[0040] to [0046] of commonly assigned U.S. Patent Application Pub. No.2003/0236514, the entire disclosure of which is hereby incorporated byreference.

The stent 40 may include radiopaque elements or include a radiopaquematerial to permit visualization of placement of the stent 40 with afluoroscopy device, or other imaging technique. For example, thepolymeric material forming the stent 40 may include iodine, or ametallic powder, such as tungsten or barium may be dispersed in thepolymeric material forming the stent 40 to provide the stent 40 with adesired degree of radiopacity.

The stent 40 may be positioned on the balloon structure 20 such that thestent 40 surrounds a body portion 52 of the inflatable balloon structure20, with a distal anchoring portion 60 of the inflatable balloonstructure 20 positioned distal of the stent 40 and a proximal anchoringportion 62 of the inflatable balloon structure 20 positioned proximal ofthe stent 40. In some instances, the distal anchoring portion 60 of theinflatable balloon structure 20 may be configured to expand within aportion of the true lumen of the blood vessel distal of the occlusionand/or the proximal anchoring portion 62 of the inflatable balloonstructure 20 may be configured to expand within a portion of the truelumen of the blood vessel proximal of the occlusion to anchor therecanalization catheter 10 from unintentional movement during expansionof the stent 40 in a subintimal pathway.

As shown in FIG. 1, in some instances, the body portion 52 may be adilatation balloon 50, while the distal anchoring portion 60 may be adistal cone portion 54 of the dilatation balloon 50 extending betweenthe body portion 52 and a distal waist of the dilatation balloon 50,and/or the proximal anchoring portion 62 may be a proximal cone portion56 of the dilatation balloon 50 extending between the body portion 52and a proximal waist of the dilatation balloon 50.

The distal anchoring portion 60 and/or the proximal anchoring portion 62may be sufficiently sized and configured to anchor the recanalizationcatheter 10 in the vasculature to prevent unintentional displacement ofthe stent 40 in a subintimal pathway during deployment (e.g., expansion)of the stent 40 in the subintimal pathway.

For example, in an inflated configuration in which the body portion 52is inflated to expand the stent 40 into an expanded configuration, asshown in FIG. 1, the distal anchoring portion 60 of the inflatableballoon structure 20 may have an outer diameter in the inflatedconfiguration greater than an outer diameter of the stent 40 in theexpanded configuration. Thus, as the stent 40 is expanded against vesselwall tissue defining the subintimal pathway, the diameter of the distalanchoring portion 60 may be sufficiently larger than the expandeddiameter of the stent 40 to prevent displacement of the distal anchoringportion 60 proximally into the subintimal pathway from the true lumendistal of the occlusion.

Similarly, in an inflated configuration in which the body portion 52 isinflated to expand the stent 40 into an expanded configuration, as shownin FIG. 1, the proximal anchoring portion 62 of the inflatable balloonstructure 20 may have an outer diameter in the inflated configurationgreater than an outer diameter of the stent 40 in the expandedconfiguration. Thus, as the stent 40 is expanded against vessel walltissue defining the subintimal pathway, the diameter of the proximalanchoring portion 62 may be sufficiently larger than the expandeddiameter of the stent 40 to prevent displacement of the proximalanchoring portion 62 distally into the subintimal pathway from the truelumen proximal of the occlusion.

Furthermore, the length of the distal cone portion 54, forming thedistal anchoring portion 60, may extend distal of the stent 40 for adistance of at least 10% of the length or at least 20% of the length ofthe stent 40 measured from a proximal end of the stent 40 to a distalend of the stent 40. The proximal cone portion 56 may extend proximallyfrom the stent 40 in a similar fashion. For instance, the length of theproximal cone portion 56, forming the proximal anchoring portion 62, mayextend proximal of the stent 40 for a distance of at least 10% of thelength or at least 20% of the length of the stent 40 measured from aproximal end of the stent 40 to a distal end of the stent 40.Accordingly, for a stent 40 having a length of about 20 millimeters, thedistal cone portion 54 and/or the proximal cone portion 56 may extendabout 2 to about 4 millimeters beyond the ends of the stent 40, in someinstances.

The inflatable balloon structure 20 may be configured such that thedistal cone portion 54, forming the distal anchoring portion 60, and/orthe proximal cone portion 56, forming the proximal anchoring portion 62,may be at least partially inflated prior to inflating the body portion52 sufficiently to radially expand the stent 40 into the expandedconfiguration. For example, the distal cone portion 54 and/or theproximal cone portion 56 may be configured to be expanded at a lowerpressure than the body portion 52, such that as the pressure within theinflatable balloon structure 20 is increased, the distal cone portion 54and/or the proximal cone portion 56 are initially inflated to anchor theinflatable balloon structure 20, and thus the catheter 10, through thesubintimal pathway prior to radially expanding the stent 40 in thesubintimal pathway.

FIG. 2 illustrates an alternative configuration of the distal portion ofthe recanalization catheter 10. As shown in FIG. 2, the recanalizationcatheter 10 includes an inflatable balloon structure 120 mounted on thedistal portion of the catheter shaft 12.

The stent 40 may be positioned on the balloon structure 120 such thatthe stent 40 surrounds a body portion 152 of the inflatable balloonstructure 120, with a distal anchoring portion 160 of the inflatableballoon structure 120 positioned distal of the stent 40 and a proximalanchoring portion 162 of the inflatable balloon structure 120 positionedproximal of the stent 40. In some instances, the distal anchoringportion 160 of the inflatable balloon structure 120 may be configured toexpand within a portion of the true lumen of the blood vessel distal ofthe occlusion and/or the proximal anchoring portion 162 of theinflatable balloon structure 120 may be configured to expand within aportion of the true lumen of the blood vessel proximal of the occlusionto anchor the recanalization catheter 10 from unintentional movementduring expansion of the stent 40 in a subintimal pathway.

As shown in FIG. 2, the body portion 152 may be a dilatation balloon150, while the distal anchoring portion 160 may be a separate anchoringballoon 166 located on the catheter shaft 12 distal of the dilatationballoon 150. In such an embodiment, the dilatation balloon 150 may be influid communication with a first inflation lumen extending through thecatheter shaft 12 and the anchoring balloon 166 may be in fluidcommunication with a second inflation lumen extending through thecatheter shaft 12, thus permitting the anchoring balloon 166 to beinflated independent of the dilatation balloon 150. In other instances,the dilatation balloon 150 and the anchoring balloon 166 may both be influid communication with a single inflation lumen, with the anchoringballoon 166 configured to be at least partially inflated prior toinflating the dilatation balloon 150. For example, the anchoring balloon166 may be configured to be inflated at a lower inflation pressure thanthe dilatation balloon 150.

Similar to the balloon structure 20, the proximal anchoring portion 162may be a proximal cone portion 156 of the dilatation balloon 150extending between the body portion 152 and a proximal waist of thedilatation balloon 150. The dilatation balloon 150 may also include adistal cone portion 154 located distal of the stent 40 which may aid inanchoring the recanalization catheter 10.

The distal anchoring portion 160 and/or the proximal anchoring portion162 may be sufficiently sized and configured to anchor therecanalization catheter 10 in the vasculature to prevent unintentionaldisplacement of the stent 40 in a subintimal pathway during deployment(e.g., expansion) of the stent 40 in the subintimal pathway.

The anchoring balloon 166 may be a separate member from the dilatationballoon 150, or the anchoring balloon 166 may be a distal extension ofthe dilatation balloon 150, with an intermediate waist 170 of theballoon structure 120 secured to the catheter shaft 12 between thedilatation balloon 150 and the anchoring balloon 166.

FIG. 3 illustrates another alternative configuration of the distalportion of the recanalization catheter 10. As shown in FIG. 3, therecanalization catheter 10 includes an inflatable balloon structure 220mounted on the distal portion of the catheter shaft 12.

The stent 40 may be positioned on the balloon structure 220 such thatthe stent 40 surrounds a body portion 252 of the inflatable balloonstructure 220, with a distal anchoring portion 260 of the inflatableballoon structure 220 positioned distal of the stent 40 and a proximalanchoring portion 262 of the inflatable balloon structure 220 positionedproximal of the stent 40. In some instances, the distal anchoringportion 260 of the inflatable balloon structure 220 may be configured toexpand within a portion of the true lumen of the blood vessel distal ofthe occlusion and/or the proximal anchoring portion 262 of theinflatable balloon structure 220 may be configured to expand within aportion of the true lumen of the blood vessel proximal of the occlusionto anchor the recanalization catheter 10 from unintentional movementduring expansion of the stent 40 in a subintimal pathway.

As shown in FIG. 3, the body portion 252 may be a dilatation balloon250, while the distal anchoring portion 260 may be a separate anchoringballoon 266 located on the catheter shaft 12 distal of the dilatationballoon 250. In such an embodiment, the dilatation balloon 250 may be influid communication with a first inflation lumen extending through thecatheter shaft 12 and the anchoring balloon 266 may be in fluidcommunication with a second inflation lumen extending through thecatheter shaft 12, thus permitting the anchoring balloon 266 to beinflated independent of the dilatation balloon 250. In other instances,the dilatation balloon 250 and the anchoring balloon 266 may both be influid communication with a single inflation lumen, with the anchoringballoon 266 configured to be at least partially inflated prior toinflating the dilatation balloon 250. For example, the anchoring balloon266 may be configured to be inflated at a lower inflation pressure thanthe dilatation balloon 250.

Similar to the balloon structure 20, the proximal anchoring portion 262may be a proximal cone portion 256 of the dilatation balloon 250extending between the body portion 252 and a proximal waist of thedilatation balloon 250. The dilatation balloon 250 may also include adistal cone portion 254 located distal of the stent 40 which may aid inanchoring the recanalization catheter 10.

The distal anchoring portion 260 and/or the proximal anchoring portion262 may be sufficiently sized and configured to anchor therecanalization catheter 10 in the vasculature to prevent unintentionaldisplacement of the stent 40 in a subintimal pathway during deployment(e.g., expansion) of the stent 40 in the subintimal pathway.

The anchoring balloon 266 may be a separate member from the dilatationballoon 250, and a flexible member, such as a metallic hypotube 280having a plurality of slots or slits 282 formed therein to provide adesired amount of lateral flexibility to the hypotube 280 may extendbetween the dilatation balloon 250 and the anchoring balloon 266. Adistal waist of the dilatation balloon 250 may be secured to thehypotube 280 and a proximal waist of the anchoring balloon 266 may besecured to the hypotube 280. The hypotube 280, or other flexible member,extending between the dilatation balloon 250 and the anchoring balloon266 may provide sufficient flexibility to the catheter shaft 12 toenable the dilatation balloon 250 to be positioned and inflated in thesubintimal pathway while the anchoring balloon 266 is positioned andinflated in the true lumen of the blood vessel distal of the occlusion.

In some instances, it may be undesired, difficult or impossible to passthrough an occlusion, such as a chronic total occlusion (CTO) in a lumenof a blood vessel with a medical device to recanalize the vessel. Insuch instances, it may be possible to recanalize the blood vesselthrough a subintimal approach using the recanalization catheter 10.Accordingly, FIGS. 4-8 illustrate aspects of an exemplary method forrecanalizing a blood vessel 80 occluded by an occlusion 90 using therecanalization catheter 10.

The blood vessel 80 typically has three tissue layers, an innermostlayer or intima layer (i.e., tunica intima) 82, an intermediate layer ormedia layer (i.e., tunica media) 84, and an outermost layer oradventitia layer (tunica adventitia) 86, with the media layer 84positioned between the intima layer 82 and the adventitia layer 86. Theintima layer 82 is a layer of endothelial cells lining the lumen 88 ofthe vessel 80, as well as a subendothelial layer made up of mostly looseconnective tissue. The media layer 84 is a muscular layer formedprimarily of circumferentially arranged smooth muscle cells. Theadventitia layer 86, which forms the exterior layer of the vessel wall80 is formed primarily of loose connective tissue made up of fibroblastsand associated collagen fibers.

As shown in FIG. 4, a subintimal pathway within the wall of the bloodvessel 80 may initially be established to bypass the occlusion 90. Asused herein, a subintimal pathway or space is a space between the intimalayer 82 and the adventitia layer 86 created in the vessel wall 80, suchas through dissection of the tissue layers of the vessel wall 80. Forexample, a guidewire 22 may initially be advanced through the lumen 88of the vessel 80 to a location proximate a proximal end of an occlusion90 blocking the lumen 88. The guidewire 22 may then be advanced topenetrate outward through the intima layer 82 at a location proximal ofthe proximal end of the occlusion 90 into the vessel wall 80. With thetip of the guidewire 22 located between the intima layer 82 and theadventitia layer 86, the guidewire 22 may be further advanced distallyin a subintimal manner to create a subintimal space between the intimalayer 82 and the adventitia layer 86. The guidewire 22 may be advancedin a subintimal manner until the distal tip of the guidewire 22 islocated distal of the distal end of the occlusion 90 in the subintimalspace created, such as by dissection of the tissue layers of the vesselwall 80. Once past the occlusion 90, the guidewire 22 may be directedback into the true lumen of the blood vessel 80 distal of the occlusion90. Accordingly, the guidewire 22 may establish a subintimal trackaround the occlusion 90 from the true lumen proximal of the occlusion 90to the true lumen distal of the occlusion 90 over which an additionalmedical device may be advanced to perform a medical procedure within thevasculature.

It is recognized that other techniques may be implemented in order tosubintimally bypass an occlusion 90 with a guidewire or otherwiseestablish a subintimal track around the occlusion 90. For example, are-entry catheter or other tissue penetrating device may be utilized toassist re-entering the true lumen distal of the occlusion 90 if needed.

As shown in FIG. 5, the recanalization catheter 10 may then be advanceddistally over the guidewire 22 from the true lumen 88 proximal of theocclusion 90, into the subintimal space between the intima layer 82 andthe adventitia layer 86. The distal end of the recanalization catheter10 may re-enter the true lumen distal of the occlusion 90, such that thebody portion 52 of the balloon structure 20, with the stent 40positioned thereon, may be positioned across the occlusion in thesubintimal path. The recanalization catheter 10 may be advanced throughthe subintimal space in a delivery configuration, such as with theballoon structure 20 in a deflated, folded configuration with the stent40 surrounding the folded balloon structure 20.

The recanalization catheter 10 may be positioned, such that the distalend of the stent 40 opens out to and/or extends into a distal true lumenportion of the vessel 80 distal of the occlusion 90, while the proximalend of the stent 40 opens out to and/or extends into a proximal truelumen portion of the vessel 80 proximal of the occlusion 90.Accordingly, the distal anchoring portion 60 of the balloon structure 20may be positioned distal of the stent 40 in the true lumen distal of theocclusion 90 while the proximal anchoring portion 62 of the balloonstructure 20 may be positioned proximal of the stent 40 in the truelumen proximal of the occlusion 90.

Once positioned through the subintimal pathway, the balloon structure 20may be inflated with an inflation medium directed through an inflationlumen of the catheter shaft 12 to radially expand the stent 40 in thesubintimal pathway, and thus maintain a pathway for subsequent bloodflow around the occlusion 90. As shown in FIG. 6, the distal anchoringportion 60 may be inflated in the true lumen 88 distal of the occlusion90 to anchor the inflatable balloon structure 20, including the bodyportion 52 underlying the stent 40, from unintentional proximal movementwhile the stent 40 is expanded in the subintimal pathway to maintainproper placement of the stent 40 in the subintimal pathway. Additionallyor alternatively, the proximal anchoring portion 62 may be inflated inthe true lumen 88 proximal of the occlusion 90 to anchor the inflatableballoon structure 20, including the body portion 52 underlying the stent40, from unintentional distal movement while the stent 40 is expanded inthe subintimal pathway to maintain proper placement of the stent 40 inthe subintimal pathway. For instance, as can bee seen from FIG. 6, thedistal anchoring portion 60 may be inflated against an intimal wall ofthe true lumen distal of the occlusion 90 and/or the proximal anchoringportion 62 may be inflated against an intimal wall of the true lumenproximal of the occlusion 90.

The distal anchoring portion 60 may be inflated to a diameter greaterthan the diameter of the distal opening of the subintimal pathwayopening out to the true lumen distal of the occlusion 90 and/or theproximal anchoring portion 62 may be inflated to a diameter greater thanthe diameter of the proximal opening of the subintimal pathway openingout to the true lumen proximal of the occlusion 90. Thus, in theexpanded state, the distal anchoring portion 60 may be prevented frombeing drawn into the subintimal space and/or the proximal anchoringportion 62 may be prevented from being drawn into the subintimal space,anchoring the balloon structure 20 in a desired position. Accordingly,the expandable stent 40 may have an expanded diameter in the subintimalpathway less than the diameter of the distal anchoring portion 60 and/orthe proximal anchoring portion 62 of the inflatable balloon structure 20in an inflated configuration.

In some instances, the distal anchoring portion 60 and/or the proximalanchoring portion 62 may be at least partially inflated prior toinflating the body portion 52 of the inflatable balloon structure 20.For example, the distal anchoring portion 60 and/or the proximalanchoring portion 62 may be inflated to a diameter greater than thediameter of the distal opening and the proximal opening, respectively,of the subintimal pathway prior to appreciable radial expansion of thestent 40 by the body portion 52 in the subintimal space.

In some embodiments, the distal anchoring portion 60 and/or the proximalanchoring portion 62 may be configured to be expanded at a lowerpressure than the body portion 52, such that as the pressure within theinflatable balloon structure 20 is increased, the distal anchoringportion 60 and/or the proximal anchoring portion 62 are initiallyinflated to anchor the inflatable balloon structure 20, and thus thecatheter 10, through the subintimal pathway prior to radially expandingthe stent 40 in the subintimal pathway. Additionally or alternatively,the distal anchoring portion 60 and/or the proximal anchoring portion 62may be molded or heat set to a desired shape, such that as theinflatable balloon structure 20 is pressurized, the distal anchoringportion 60 and/or the proximal anchoring portion 62 are inflated to adiameter sufficient to anchor the inflatable balloon structure 20, andthus the catheter 10, through the subintimal pathway prior to radiallyexpanding the stent 40 in the subintimal pathway.

In other embodiments, the distal anchoring portion 60 and/or theproximal anchoring portion 62 may be inflated independent of inflatingthe body portion 52 of the inflatable balloon structure 20. For example,a separate inflation lumen may be in communication with each of thedistal anchoring portion 60, the proximal anchoring portion 62 and/orthe body portion 52 of the balloon structure 20. Thus, the distalanchoring portion 60 and/or the proximal anchoring portion 62 may beinflated prior to inflating the body portion 52 of the inflatableballoon structure 20.

Once the stent 40 has been expanded, the balloon structure 20 may bedeflated and the catheter 10 may be withdrawn proximally, leaving thestent 40 in the subintimal space in a radially expanded configuration.In some instances, the guidewire 22 may be retained through thesubintimal space and in the true lumen distal of the occlusion 90 toguide additional medical devices to a further treatment site distal ofthe occlusion 90. Once the procedure is complete, the guidewire 22 maybe withdrawn from the patient. FIG. 7 illustrates the radially expandedstent 40 forming a subintimal pathway 96 around the occlusion 90immediately following a surgical procedure to implant the stent 40. Thestent 40 may provide a scaffold structure supporting the subintimalpathway 96 to maintain patency for blood flow therethrough. Thesubintimal pathway 96 connects a true lumen portion of the vessel 80proximal of the occlusion 90 to a true lumen portion of the vessel 80distal of the occlusion 90 to create a by-pass for blood flow around theocclusion 90, and thus recanalize the vessel 80.

In some instances, the stent 40, which may be a bioabsorbable stentand/or include a biological coating to promote tissue growth, may beconfigured to promote native tissue regrowth around the stent 40 over aperiod of days, weeks or months to create a superficial intimal layeralong the subintimal pathway 96. For instance, as shown in FIG. 8, overa period of time after the stent 40 has been implanted in the subintimalspace, a superficial intimal layer 92 may develop to define thesubintimal pathway 96. In other words, a circumferential superficialintimal layer 92 may be formed on the luminal surface of the subintimalpathway 96 from the proximal opening to the subintimal pathway 96 to thedistal opening to the subintimal pathway 96. For example, as can be seenfrom the cross-sectional view of FIG. 8A, a circumferential superficialintimal layer 92 may be created between the intimal tissue layer 82defining the true lumen 88 of the blood vessel 80 and the adventitialtissue layer 86 of the blood vessel 80. In some instances, thecircumferential superficial intimal layer 92 may be created through themedial tissue layer 84 of the blood vessel 80. Thus, the superficialintimal layer 92 may be surrounded by tissue of the medial tissue layer84, between the intimal tissue layer 82 defining the true lumen 88 ofthe blood vessel 80 and the adventitial tissue layer 86 of the bloodvessel 80.

In some embodiments, the stent 40, or a portion thereof, may bebioabsorbable such that the stent 40 may be absorbed by the patient'sbody over a period of time, leaving the superficial intimal layer 92forming the luminal surface of the subintimal pathway 96 around theocclusion 90. Thus, over a period of time, such as days, weeks ormonths, the stent 40 may be dissolved and leave behind a functioningvessel lumen around the occlusion 90 with native tissue creating acircumferential superficial intimal layer 92 adjacent to the occludedtrue lumen 88.

Those skilled in the art will recognize that aspects of the presentdisclosure may be manifested in a variety of forms other than thespecific embodiments described and contemplated herein. Accordingly,departure in form and detail may be made without departing from thescope and spirit of the present disclosure as described in the appendedclaims.

What is claimed is:
 1. A recanalization catheter assembly forestablishing a subintimal pathway around an occlusion in a blood vessel,the recanalization catheter assembly comprising: an elongate cathetershaft extending distally from a hub assembly; an inflatable balloonstructure mounted on a distal portion of the catheter shaft, theinflatable balloon structure configured to be expanded from a deflatedconfiguration to an inflated configuration with a fluid delivered to aninterior of the inflatable balloon structure through an inflation lumenextending through the catheter shaft; a stent surrounding a body portionof the inflatable balloon structure, with a distal anchoring portion ofthe inflatable balloon structure positioned distal of the stent; whereinthe distal anchoring portion of the inflatable balloon structure isconfigured to expand within a true lumen portion of the blood vesseldistal of the occlusion to anchor the recanalization catheter fromunintentional movement during expansion of the stent in the subintimalpathway.
 2. The recanalization catheter assembly of claim 1, wherein thedistal anchoring portion of the inflatable balloon structure has anouter diameter in the inflated configuration greater than an outerdiameter of the stent in an expanded configuration.
 3. Therecanalization catheter assembly of claim 1, wherein the stent has alength measured from a proximal end of the stent to a distal end of thestent, wherein the distal anchoring portion of the inflatable balloonstructure extends distal of the stent for a distance of at least 10% ofthe length of the stent.
 4. The recanalization catheter assembly ofclaim 1, wherein the stent has a length measured from a proximal end ofthe stent to a distal end of the stent, wherein the distal anchoringportion of the inflatable balloon structure extends distal of the stentfor a distance of at least 20% of the length of the stent.
 5. Therecanalization catheter assembly of claim 1, wherein the distalanchoring portion of the inflatable balloon structure is inflatableindependent of inflation of the body portion of the inflatable balloonstructure.
 6. The recanalization catheter assembly of claim 5, whereinthe distal anchoring portion is an anchoring balloon and the bodyportion is a dilatation balloon distinct from the anchoring balloon. 7.The recanalization catheter assembly of claim 6, further comprising aslotted tubular member extending between the dilatation balloon and theanchoring balloon.
 8. The recanalization catheter assembly of claim 1,wherein the inflatable balloon structure includes a proximal anchoringportion positioned proximal of the stent configured to expand within atrue lumen portion of the blood vessel proximal of the occlusion toanchor the recanalization catheter from unintentional movement duringexpansion of the stent in the subintimal pathway.
 9. The recanalizationcatheter assembly of claim 1, wherein the body portion is a dilatationballoon and the distal anchoring portion is a distal cone portion of thedilatation balloon.
 10. A method of recanalizing a blood vessel byestablishing a subintimal pathway around an occlusion, the methodcomprising: creating a subintimal pathway between a proximal openinginto a vessel wall proximal of an occlusion and a distal opening intothe vessel wall distal of the occlusion; positioning an expandable stentin the subintimal pathway; expanding the expandable stent in thesubintimal pathway; and promoting native tissue regrowth around thestent to create a superficial intimal layer along the subintimalpathway.
 11. The method of claim 10, wherein expanding the expandablestent comprises: inflating a body portion of an inflatable balloonstructure within the expandable stent to radially expand the expandablestent.
 12. The method of claim 10, wherein the inflatable balloonstructure includes an inflatable anchoring portion configured to beinflated in a true lumen portion of the blood vessel distal of theocclusion.
 13. The method of claim 10, wherein the superficial intimallayer is created between an intimal tissue layer defining a true lumenof the blood vessel and an adventitial tissue layer of the blood vessel.14. A method of recanalizing a blood vessel by establishing a subintimalpathway around an occlusion, the method comprising: creating asubintimal pathway between a proximal opening into a vessel wallproximal of an occlusion and a distal opening into the vessel walldistal of the occlusion; positioning an expandable stent surrounding abody portion of an inflatable balloon structure in the subintimalpathway with a distal anchoring portion of the inflatable balloonstructure positioned in a true lumen portion of the blood vessel distalof the occlusion; inflating the distal anchoring portion of theinflatable balloon structure in the true lumen portion distal of theocclusion; and inflating the body portion of the inflatable balloonstructure to expand the expandable stent in the subintimal pathway;wherein the inflated distal anchoring portion anchors the inflatableballoon structure from unintentional proximal movement while the stentis expanded in the subintimal pathway to maintain proper placement ofthe stent in the subintimal pathway.
 15. The method of claim 14, whereinthe expandable stent has an expanded diameter in the subintimal pathwayless than a diameter of the distal anchoring portion of the inflatableballoon structure in an inflated configuration.
 16. The method of claim14, wherein the distal anchoring portion is inflated against an intimalwall of the true lumen distal of the occlusion.
 17. The method of claim14, wherein the distal anchoring portion is at least partially inflatedprior to inflating the body portion of the inflatable balloon structure.18. The method of claim 14, wherein the distal anchoring portion isinflated independent of inflating the body portion of the inflatableballoon structure.
 19. The method of claim 14, further comprising:inflating a proximal anchoring portion of the inflatable balloonstructure in a true lumen portion proximal of the occlusion; wherein theinflated proximal anchoring portion anchors the inflatable balloonstructure from unintentional distal movement while the stent is expandedin the subintimal pathway to maintain proper placement of the stent inthe subintimal pathway.
 20. The method of claim 19, wherein the proximalanchoring portion is at least partially inflated prior to inflating thebody portion of the inflatable balloon structure.